The meaning of petroleum product viscosity

Thread Content

Viscosity is a measure of a fluid’s viscosity, representing the force exerted by fluid flow due to internal friction. High viscosity indicates high internal friction; the greater the molecular weight, the more carbon-hydrogen bonds there are, and thus the greater this force becomes. Viscosity is decisive for various lubricants in terms of quality identification and application determination, as well as for the combustion performance and efficiency of various fuel oils. At the same distillation temperature, petroleum products with alkanes as their main components have low viscosity and good viscosity-temperature behavior, that is, a high viscosity index; in other words, the change in viscosity due to temperature variations is small ； Oils with a higher content of naphthenic (or aromatic) components have higher viscosity, that is, they exhibit poorer viscosity-temperature behavior ； Oils with high levels of gums and aromatics have high viscosity*, the worst viscosity-temperature behavior, that is, the lowest viscosity index. Viscosity is commonly expressed as dynamic viscosity, with the unit of mm2/s. Heavy fuel oil has high viscosity; preheating it to a dynamic viscosity of 18–20 mm2/s (at 40°C) facilitates uniform fuel injection by the injectors. For viscosity testing, the A1011 automatic kinematic viscosity tester can be used